Aqueous resin dispersion composition and process for producing the same

ABSTRACT

The present invention provides an aqueous resin dispersion composition prepared by neutralizing an acid-modified chlorinated polyolefin with a basic substance and dispersing the neutralized acid-modified chlorinated polyolefin in water; and a process for producing an aqueous resin dispersion composition comprising the steps of dissolving an acid-modified chlorinated polyolefin in an ethereal solvent, neutralizing the acid-modified chlorinated polyolefin by a basic substance, dispersing the neutralized acid-modified chlorinated polyolefin in water, and removing the ethereal solvent.

TECHNICAL FIELD

The present invention relates to an aqueous resin dispersion compositionfor use as a primer for substrates made of polypropylene and likepolyolefin resins and to a process for producing the same.

BACKGROUND ART

Polypropylene and like polyolefin resins have noteworthy properties andare inexpensive. Therefore, they are used in a wide variety ofapplications such as automotive parts. However, since polyolefin resinsare crystalline and their surfaces are non-polar, polyolefin resins havethe problem in that it is difficult to coat or bond them.

For this reason, chlorinated polyolefins are used to coat and bondpolyolefin resins. However, the use of toluene, xylene and like organicsolvents to dissolve such chlorinated polyolefin resins gives seriousenvironmental and health problems.

To rectify these problems, chlorinated polyolefins are often madeaqueous. However, the use of emulsifiers during production ofconventional aqueous chlorinated polyolefin resin compositions posesproblems in that the foaming of resin compositions occurs duringconcentration carried out by evaporating organic solvents and the like,thereby prolonging the production process, and emulsifiers that mayremain in films formed from resin compositions impair the waterresistance of the films. Moreover, nonylphenyl ether-type emulsifiersare often used, from which nonylphenol is generated in the process ofbiodegradation. Nonylphenol can affect the living body as an endocrinedisrupter.

DISCLOSURE OF THE INVENTION

One object of the invention is to provide an aqueous chlorinatedpolyolefin resin dispersion composition without the use of emulsifiers.

Other objects and characteristics of the present invention will becomeevident by the disclosure provided hereinbelow.

The inventors, as a result of their extensive research, found thatacid-modified chlorinated polyolefins can be dispersed in water withoutemulsifiers by using an ethereal solvent and a basic substance, andthereby accomplished the present invention.

In particular, the present invention provides an aqueous resindispersion composition and a process for producing it as describedbelow:

1. An aqueous resin dispersion composition prepared by neutralizing anacid-modified chlorinated polyolefin with a basic substance anddispersing the neutralized acid-modified chlorinated polyolefin inwater.

2. The composition according to Item 1, wherein the acid-modifiedchlorinated polyolefin is prepared by graft-copolymerizing at least onemember selected from the group consisting of α,β-unsaturated carboxylicacids and acid anhydrides thereof with at least one member selected fromthe group consisting of polypropylene and propylene-α-olefin copolymersin a proportion of 0.1 to 10 wt. % based on the at least one memberselected from the group consisting of polypropylene andpropylene-α-olefin copolymers.

3. The composition according to Item 1 or 2, wherein the acid-modifiedchlorinated polyolefin has a chlorine content of 15 to 35 wt. %.

4. The composition according to any one of Items 1 to 3, wherein theacid-modified chlorinated polyolefin has a weight-average molecularweight of 10000 to 150000.

5. The composition according to any one of Items 1 to 4, wherein thebasic substance is at least one member selected from the groupconsisting of morpholine, ammonia and amines.

6. A process for producing an aqueous resin dispersion compositioncomprising the steps of:

-   -   dissolving an acid-modified chlorinated polyolefin in an        ethereal solvent;    -   adding a basic substance to the acid-modified chlorinated        polyolefin to neutralize;    -   adding water to disperse the neutralized acid-modified        chlorinated polyolefin therein; and    -   removing the ethereal solvent.

7. The process according to Item 6, wherein the acid-modifiedchlorinated polyolefin is prepared by graft-copolymerizing at least onemember selected from the group consisting of α,β-unsaturated carboxylicacids and acid anhydrides thereof with at least one member selected fromthe group consisting of polypropylene and propylene-α-olefin copolymersin a proportion of 0.1 to 10 wt. % based on the at least one memberselected from the group consisting of polypropylene andpropylene-α-olefin copolymers.

8. The process according to Item 6 or 7, wherein the acid-modifiedchlorinated polyolefin has a chlorine content of 15 to 35 wt. %.

9. The process according to any one of Items 6 to 8, wherein theacid-modified chlorinated polyolefin has a weight-average molecularweight of 10000 to 150000.

10. The process according to any one of Items 6 to 9, wherein theethereal solvent is at least one member selected from the groupconsisting of tetrahydrofuran, propylene glycol monomethyl ether,propylene glycol monoethyl ether and propylene glycol monopropyl ether.

11. The process according to any one of Items 6 to 10, wherein the basicsubstance is at least one member selected from the group consisting ofmorpholine, ammonia and amines.

The aqueous resin dispersion composition and the production processthereof of the present invention are described below in detail.

To produce the aqueous resin dispersion composition of the invention, anacid-modified chlorinated polyolefin is dissolved in an etherealsolvent, the acid-modified chlorinated polyolefin is neutralized byadding a basic substance, water is added to disperse the neutralizedacid-modified chlorinated polyolefin therein, and the ethereal solventis removed.

With respect to the starting material, i.e., acid-modified chlorinatedpolyolefin, those that can be prepared by, for example,graft-copolymerizing at least one member selected from α,β-unsaturatedcarboxylic acids and acid anhydrides thereof with at least one memberselected from polypropylene and propylene-α-olefin copolymers, andchlorinating thus-prepared acid-modified polyolefin are usable.

Propylene-α-olefin copolymers as used herein are compounds that containpropylene as a principal ingredient copolymerized with at least oneother α-olefin. Examples of other α-olefins include ethylene, 1-butene,1-heptene, 1-octene, 4-methyl-1-pentene, etc., and they can be usedsingly or in combination. Among such α-olefins, ethylene and 1-buteneare preferable. Although the ratio of propylene to other α-olefin(s) inthe propylene-α-olefin copolymer is not limited, propylene is containedpreferably in a proportion of 50 mol % or greater, and more preferably90 mol % or greater.

Examples of α,β-unsaturated carboxylic acids and acid anhydrides thereofthat are to be graft-copolymerized with at least one member selectedfrom polypropylene and propylene-α-olefin copolymers include maleicacid, itaconic acid, citraconic acid, and the acid anhydrides thereof.Among these, acid anhydrides are preferable, with maleic anhydride anditaconic anhydride being particularly preferable. The at least onemember selected from α,β-unsaturated carboxylic acids and acidanhydrides thereof is graft-copolymerized in a proportion of 0.1 to 10wt. % and more preferably 1 to 5 wt. %.

Examples of methods for graft-copolymerizing the at least one memberselected from α,β-unsaturated carboxylic acids and acid anhydridesthereof with the at least one member selected from polypropylene andpropylene-α-olefin copolymers include solution methods, fusion methodsand like known methods.

For example, a solution method can be carried out as follows. At leastone member selected from polypropylene and propylene-α-olefin copolymersis dissolved in an aromatic organic solvent such as toluene at 100 to180° C.; at least one member selected from α,β-unsaturated carboxylicacids and acid anhydrides thereof is added thereto; and a reaction isproceeded by adding a radical generator in a single batch or inportions.

For example, a fusion method can be carried out as follows. At least onemember selected from polypropylene and propylene-α-olefin copolymers isfused by heating it to its melting point or greater, and a reaction isproceeded by adding a radical generator and at least one member selectedfrom α,β-unsaturated carboxylic acids and acid anhydrides thereof.

Examples of radical generators are benzoyl peroxide, dicumyl peroxide,di-t-butyl peroxide, etc. Radical generators can be suitably selectedaccording to their decomposition temperature and the reactiontemperature.

The acid-modified polyolefin obtained as above is then chlorinated togive an acid-modified chlorinated polyolefin.

Such chlorination can be performed by, for example, dissolving theacid-modified polyolefin in a chlorinated solvent and injecting chlorinegas in the presence or absence of a radical generator such that theacid-modified polyolefin acquires a chlorine content of 15 to 35 wt. %.Examples of chlorinated solvents are tetrachloroethylene,tetrachloroethane, carbon tetrachloride, chloroform, etc.

The acid-modified chlorinated polyolefin has a chlorine content ofpreferably 15 to 35 wt. %. Acid-modified chlorinated polyolefins havinga chlorine content of less than 15 wt. % may not be able to be dispersedin water due to their poor solubility qualities. Acid-modifiedchlorinated polyolefins having a chlorine content of greater than 35 wt.% may exhibit inferior adhesion due to their poor cohesion. A morepreferable chlorine content is 17 to 27 wt. %.

The acid-modified chlorinated polyolefin has a weight-average molecularweight of preferably 10000 to 150000. Acid-modified chlorinatedpolyolefins having a weight-average molecular weight of less than 10000may exhibit inferior adhesion due to their poor cohesion. Acid-modifiedchlorinated polyolefins having a weight-average molecular weight ofgreater than 150000 may not be able to be dispersed in water due totheir poor solubility qualities. A more preferable weight-averagemolecular weight is 30000 to 100000. The weight-average molecular weightcan be measured by GPC (gel permeation chromatography).

To produce the aqueous resin dispersion composition of the invention,the acid-modified chlorinated polyolefin is dissolved in an etherealsolvent, neutralized by adding a basic substance, dispersed in water,and the ethereal solvent is then removed.

The production process is described step by step below.

Initially, the acid-modified chlorinated polyolefin is dissolved in anethereal solvent. Examples of ethereal solvents are tetrahydrofuran,propylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol monopropyl ether, etc. Such ethereal solvents can beused singly or in combination. Preferable ethereal solvents aretetrahydrofuran and propylene glycol monopropyl ether. The weight ratioof acid-modified chlorinated polyolefin/ethereal solvent is preferably60/40 to 10/90, and more preferably 40/60 to 10/90. Although thedissolution temperature is not limited, it is preferably about 50 toabout 65° C.

Next, the acid-modified chlorinated polyolefin solution obtained aboveis neutralized by adding a basic substance. Examples of basic substancesinclude morpholine; ammonia; and methylamine, ethylamine, dimethylamine,triethylamine, ethanolamine, dimethylethanolamine and like amines. Suchbasic substances can be used singly or in combination. A preferablebasic substance is dimethylethanolamine. The amount of basic substanceused is preferably 1 to 2.5 chemical equivalents and more preferably 1.5to 2.5 chemical equivalents per carboxyl group of the acid-modifiedchlorinated polyolefin.

Next, water is added to the neutralized acid-modified chlorinatedpolyolefin solution to form a W/O dispersion. Water is further added toinitiate phase conversion to give an O/W dispersion. Although thetemperature of water to be added is not limited, it is preferably about50 to about 70° C. The amount of water to be added is also not limited,but it is preferably 2 to 6 times and more preferably 3 to 5 times theweight of the acid-modified chlorinated polyolefin. In the presentinvention, an ethereal solvent can be added in conjunction with watersuch that the weight ratio of acid-modified chlorinatedpolyolefin/ethereal solvent in the dispersion is within the range offrom 40/60 to 10/90. The makeup (weight ratio) of the dispersion afterphase conversion is preferably acid-modified chlorinatedpolyolefin/ethereal solvent/basic substance/water of1/0.4-3.5/0.07-0.25/4-9.

Thereafter, the aqueous resin dispersion composition of the invention isobtained by removing the ethereal solvent from the phase-converteddispersion. Reduced-pressure distillation can be employed to remove theethereal solvent. Although the degree of pressure reduction duringdistillation is not limited, a reduced pressure of about 90 to about 95kPa is preferable. In this instance, water is partially evaporated. Themakeup (weight ratio) of the aqueous resin dispersion composition afterdistilling off the ethereal solvent and part of water under reducedpressure is preferably acid-modified chlorinated polyolefin/basicsubstance/water of 1/0.06-0.33/1.5-4. Water can be replenished in asuitable amount as necessary.

The aqueous resin dispersion composition of the invention can be usedsingly or in combination with pigments or other aqueous resins.

The aqueous resin dispersion composition of the invention has excellentadhesion to polyolefin resins, and therefore is useful in applicationssuch as primers for coating and bonding as well as coating materials andadhesives.

The aqueous resin dispersion composition of the invention has excellentadhesion to polypropylene and like polyolefin resins, outstandinggasoline resistance, and remarkable water resistance.

According to the production process of the invention, an aqueouschlorinated polyolefin resin dispersion composition can be obtainedwithout the use of an emulsifier.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples and a Comparative Example are given below to illustrate theinvention in more detail.

EXAMPLE 1

Thirty grams of an acid-modified chlorinated polyolefin (propylenecontent in the propylene-ethylene copolymer: 94.5 mol %,graft-copolymerized maleic anhydride content: 2.0 wt. %, chlorinecontent: 21.1 wt. %, weight-average molecular weight: 51000) and 70 g oftetrahydrofuran were placed in a stirrer-equipped flask and heated to65° C. to dissolve. Then, 0.94 g (2 chemical equivalents) ofdimethylethanolamine was added. While maintaining the temperature at 65°C., water at 60° C. was added dropwise. Addition of 100 g of waterconverted the dispersion from W/O to O/W. Tetrahydrofuran was distilledoff for 1 hour under reduced pressure at 93 kPa, thereby giving a milkywhite dispersion (aqueous resin dispersion composition). This dispersionhad a solids content of 30 wt. %. After being left to stand for 1 week,this dispersion did not exhibit separation.

EXAMPLE 2

Thirty grams of an acid-modified chlorinated polyolefin (propylenecontent in the propylene-ethylene copolymer: 97.5 mol %,graft-copolymerized maleic anhydride content: 1.2 wt. %, chlorinecontent: 20.1 wt. %, weight-average molecular weight: 85000), 56 g oftetrahydrofuran and 14 g of propylene glycol monopropyl ether wereplaced in a stirrer-equipped flask and heated to 65° C. to dissolve.Then, 0.56 g (2 chemical equivalents) of dimethylethanolamine was added.While maintaining the temperature at 65° C., water at 60° C. was addeddropwise. Addition of 100 g of water converted the dispersion from W/Oto O/W. Tetrahydrofuran and propylene glycol monopropyl ether weredistilled off for 1.5 hours under reduced pressure at 92 kPa, therebygiving a milky white dispersion (aqueous resin dispersion composition).This dispersion had a solids content of 30 wt. %. After being left tostand for 1 week, this dispersion did not exhibit separation.

COMPARATIVE EXAMPLE 1

Thirty grams of an acid-modified chlorinated polyolefin (propylenecontent in the propylene-ethylene copolymer: 94.5 mol %,graft-copolymerized maleic anhydride content: 2.0 wt. %, chlorinecontent: 21.1 wt. %, weight-average molecular weight: 51000) and 70 g oftetrahydrofuran were placed in a stirrer-equipped flask and heated to65° C. to dissolve. Then, 6 g of a nonionic emulsifier was added andstirred, and 0.94 g (2 chemical equivalents) of dimethylethanolamine wasfurther added. While maintaining the temperature at 65° C., water at 60°C. was added dropwise. Addition of 100 g of water converted thedispersion from W/O to O/W. Tetrahydrofuran was distilled off for 2.5hours under reduced pressure at 93 kPa, thereby giving a milky whitedispersion (aqueous resin dispersion composition). This dispersion had asolids content of 31 wt. %. After being left to stand for 1 week, thisdispersion did not exhibit separation.

The adhesion, gasoline resistance and water resistance of the aqueousresin dispersion compositions obtained in Examples 1 and 2 andComparative Example 1 were evaluated according to the methods describedbelow:

Adhesion: Polypropylene boards were coated with the aqueous resindispersion compositions which had a solids content of 30 wt. % and driedat 80° C. for 10 minutes. A two-component urethane coating was furtherapplied thereonto and the boards were dried at 90° C. for 20 minutes.The coated surface of each board was provided with a grid pattern ofhundred 1-mm squares by a cutter. An adhesive cellophane tape wassecurely placed on the coated surface, and the tape was quickly peeledparallel to the surface. This procedure was repeated 10 times. If acoated board exhibited no film removal after ten rounds of tape peeling,this was given 10 points.

Gasoline resistance: Coated boards were prepared in the same manner asabove and immersed in conventional unleaded gasoline maintained at 20°C. for 2 hours. Good refers to the coated surface staying intact. Poorrefers to peeling of the coated surface occurring.

Water resistance: Coated boards were prepared in the same manner asabove and immersed in 40° C. warm water for 10 days. Good refers to thecoated surface staying intact. Poor refers to blisters being created onthe coated surface.

Table 1 shows the results of the evaluations. TABLE 1 Adhesion Gasolineresistance Water resistance Ex. 1 10 Good Good Ex. 2 10 Good Good Comp.10 Good Poor Ex. 1

1. An aqueous resin dispersion composition prepared by neutralizing witha basic substance an acid-modified chlorinated polyolefin that has beenmodified by at least one member selected from the group consisting ofmaleic acid, itaconic acid, citraconic acid, and acid anhydridesthereof, and dispersing the neutralized acid-modified chlorinatedpolyolefin in water.
 2. The composition according to claim 1, whereinthe acid-modified chlorinated polyolefin is prepared bygraft-copolymerizing at least one member selected from the groupconsisting of maleic acid, itaconic acid, citraconic acid, and acidanhydrides thereof with at least one member selected from the groupconsisting of polypropylene and propylene-α-olefin copolymers in aproportion of 0.1 to 10 wt. % based on the at least one member selectedfrom the group consisting of polypropylene and propylene-α-olefincopolymers.
 3. The composition according to claim 1, wherein theacid-modified chlorinated polyolefin has a chlorine content of 15 to 35wt. %.
 4. The composition according to claim 1, wherein theacid-modified chlorinated polyolefin has a weight-average molecularweight of 10000 to
 150000. 5. The composition according to claim 1,wherein the basic substance is at least one member selected from thegroup consisting of morpholine, ammonia and amines.
 6. A process forproducing an aqueous resin dispersion composition comprising the stepsof: dissolving an acid-modified chlorinated polyolefin in an etherealsolvent; adding a basic substance to the acid-modified chlorinatedpolyolefin to neutralize; adding water to disperse the neutralizedacid-modified chlorinated polyolefin therein; and removing the etherealsolvent.
 7. The process according to claim 6, wherein the acid-modifiedchlorinated polyolefin is prepared by graft-copolymerizing at least onemember selected from the group consisting of α,β-unsaturated carboxylicacids and acid anhydrides thereof with at least one member selected fromthe group consisting of polypropylene and propylene-α-olefin copolymersin a proportion of 0.1 to 10 wt. % based on the at least one memberselected from the group consisting of polypropylene andpropylene-α-olefin copolymers.
 8. The process according to claim 6,wherein the acid-modified chlorinated polyolefin has a chlorine contentof 15 to 35 wt. %.
 9. The process according to claim 6, wherein theacid-modified chlorinated polyolefin has a weight-average molecularweight of 10000 to
 150000. 10. The process according to claim 6, whereinthe ethereal solvent is at least one member selected from the groupconsisting of tetrahydrofuran, propylene glycol monomethyl ether,propylene glycol monoethyl ether and propylene glycol monopropyl ether.11. The process according to claim 6, wherein the basic substance is atleast one member selected from the group consisting of morpholine,ammonia and amines.